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Türk1. Unveiling the mystery of hot melt adhesive film
In basic terms, hot melt adhesive film is a thin film adhesive made of thermoplastic polymers as the main component and processed by special technology. Its appearance varies. Some are transparent, like a thin layer of plastic paper, and the object behind can be clearly seen; some are opaque colors such as white and light yellow, with uniform and flat texture. Its thickness also varies greatly, ranging from a few microns to hundreds of microns, and can be selected according to different application scenarios.
This film-like form makes it more convenient to use, and can be cut into various shapes and sizes according to needs to meet different bonding needs. Whether it is large-area flat bonding or small-scale fine bonding, hot melt adhesive film can handle it with ease.
So, how does hot melt adhesive film achieve bonding? Its working principle is actually not complicated, and we can understand it through common phenomena in life. For example, when we use candles, when the flame is close to the candle, the solid wax will gradually melt and become liquid. When the liquid wax drips on the surface of the object, it will solidify again after a period of cooling, and can slightly stick to the surface of the object. The working principle of hot melt adhesive film is similar to this. When it is heated to a certain temperature, the originally solid film will melt quickly and become a fluid viscous fluid. This viscous fluid can well infiltrate the surface of the adhered object and fill the tiny gaps on the surface. Subsequently, in the process of lowering the temperature, the viscous fluid will quickly solidify and return to a solid state. At this time, it can tightly bond the adhered materials together to form a strong bond.
This method of bonding through temperature changes makes it unnecessary to add any solvents during the use of hot melt adhesive film, which is both environmentally friendly and efficient. Moreover, its bonding process is reversible. If the bonded materials need to be separated in subsequent processing or use, just heat it again to let the hot melt adhesive film melt again, and the separation can be easily achieved. This feature is very practical in some scenes that require rework or recycling.
2. Multiple types of hot melt adhesive film
Hot melt adhesive film is not a single product. It can be divided into multiple types according to its main ingredients. Each type has unique performance and applicable fields.
2.1 EVA hot melt adhesive film: a widely used basic model
EVA hot melt adhesive film is made of ethylene-vinyl acetate copolymer (EVA) as the main base material, and then added with various additives such as tackifiers, waxes, antioxidants, etc., through mixing, extrusion, calendaring and other processes. Among them, the content of vinyl acetate (VA) is an important factor affecting the performance of EVA hot melt adhesive film. Generally speaking, the higher the VA content, the better the flexibility, adhesion and transparency of the film, but the heat resistance will decrease; conversely, the lower the VA content, the harder and heat resistance of the film will increase, but the flexibility and adhesion will decrease.
Due to its easy availability of raw materials and relatively simple production process, the cost of EVA hot melt adhesive film is relatively low, which makes it widely used in many fields. In the packaging industry, it is an indispensable and important material. Whether it is biscuit boxes and chocolate boxes in food packaging, or shampoo boxes and washing powder bags in daily necessities packaging, EVA hot melt adhesive film can be seen. It can quickly bond packaging materials together, ensure the sealing and firmness of the packaging, and prevent the product from getting damp and scattered during transportation and storage. In the textile industry, EVA hot melt adhesive film is often used for the bonding of clothing fabrics, such as bonding the lining and the fabric together to increase the stiffness and warmth of the clothing; in the production of shoes and hats, it can bond the upper, sole, brim and other parts, replacing the traditional sewing process, which not only improves production efficiency, but also makes the product more beautiful.
2.2 PA hot melt adhesive film: the choice of pursuing high performance
PA hot melt adhesive film is made of polyamide (PA) as the main component. Polyamide is a polymer material with excellent performance, which makes PA hot melt adhesive film also have many excellent characteristics. Its melting point is relatively high, generally between 120℃ and 180℃. It has excellent temperature resistance and can maintain stable bonding strength in a high temperature environment. Even if it is used in an environment above 100℃, it is not easy to soften or fall off. At the same time, it has high bonding strength and has good adhesion to a variety of materials, especially for metals, nylon and other materials.
These characteristics make PA hot melt adhesive film widely used in some fields with high performance requirements. In the field of automotive interiors, the temperature inside the car varies greatly. In summer, under direct sunlight, the temperature inside the car may reach more than 60℃, while in winter, it will be in a lower temperature environment. PA hot melt adhesive film has become an ideal choice for automotive interior bonding due to its good temperature resistance. For example, in the production of car seats, it can bond the fabric, sponge, frame and other parts of the seat together to ensure that the seat will not have problems such as debonding and deformation during long-term use; in the assembly of door interior panels, it can firmly bond various decorative materials to the door panels to improve the beauty and comfort of the car.
PA hot melt adhesive film also plays an important role in the field of high-end shoe material manufacturing. High-end shoe materials usually have high requirements for bonding strength, temperature resistance and aging resistance to ensure the service life of shoes under long-term wear and various complex environments. PA hot melt adhesive film can meet these requirements. It can tightly bond the upper, sole, upper and other parts together, and will not debond even after long-term walking and exercise. Moreover, it has good flexibility and will not affect the comfort and flexibility of the shoes, providing a strong guarantee for the quality of high-end shoe materials.
2.3 TPU hot melt adhesive film: a versatile all-rounder with balanced performance
TPU hot melt adhesive film is made of thermoplastic polyurethane (TPU), a polymer material between plastic and rubber with many unique properties. It has excellent elasticity and can quickly recover to its original shape after being stretched by a large external force, and is not prone to permanent deformation; at the same time, it has good wear resistance and can withstand frequent friction and collision without being easily damaged; in addition, it also has good low temperature resistance, and will not become brittle or crack in an environment of dozens of degrees below zero, and still maintains good flexibility and bonding performance.
These properties make TPU hot melt adhesive film a well-balanced all-rounder with a wide range of applications in many fields. In the field of outdoor products, the outdoor environment is usually harsh, and the performance requirements of the product are high. For example, a jacket needs to have windproof, waterproof, wear-resistant and other properties. In the production of a jacket, TPU hot melt adhesive film can achieve seamless bonding between fabrics, avoiding the problem of water leakage caused by pinholes left by traditional sewing processes. At the same time, its elasticity and wear resistance can also ensure that the jacket will not be debonded due to stretching or friction during activities. In the production of tents, TPU hot melt adhesive film can bond the fabric, bracket and other parts of the tent together to ensure the sealing and firmness of the tent and resist the invasion of wind and rain.
In the field of medical supplies, TPU hot melt adhesive film also has important applications. Because it has good biocompatibility and will not irritate or allergic to human skin, it is widely used in the production of medical bandages, infusion patches, surgical gowns and other products. In the production of medical bandages, TPU hot melt adhesive film can bond the elastic fabric and the drug layer together, which can not only ensure the elasticity of the bandage and facilitate bandaging, but also ensure the stability of the drug layer so that the drug can continue to play a role; in the production of infusion patches, it can firmly bond the adhesive layer and the water-absorbing layer to ensure that the infusion patch will not fall off during use. At the same time, it has good air permeability and can reduce irritation to the skin.
2.4 PES hot melt adhesive film: a powerful assistant in the field of electronics
PES hot melt adhesive film is made of polyethersulfone (PES) as the main component. PES is a high-performance special engineering plastic with excellent heat resistance, chemical resistance and electrical insulation. It has a high glass transition temperature and can maintain stable performance in a high temperature environment above 200°C without softening or decomposition; at the same time, it has good resistance to chemical substances such as acids, alkalis, and organic solvents, and is not easily corroded; in addition, it has excellent electrical insulation properties and can effectively block current to ensure the safe operation of electronic equipment.
These characteristics make PES hot melt adhesive film a powerful assistant in the field of electronic manufacturing. In the connection of flexible circuit boards, flexible circuit boards are thin and bendable, and are widely used in electronic products such as smart phones, tablets, and wearable devices. Since flexible circuit boards generate a certain amount of heat during operation and need to be bent, folded, etc., there are extremely high requirements for the adhesive used for connection. PES hot melt adhesive film can meet these requirements. It can firmly connect different layers of flexible circuit boards or other components. Even under high temperature and frequent bending, it can maintain stable connection performance and ensure smooth transmission of electronic signals.
PES hot melt adhesive film also plays an important role in the packaging process of electronic components. Electronic components are easily affected by external factors such as dust, moisture, vibration, etc. during use, resulting in performance degradation or damage. PES hot melt adhesive film can encapsulate electronic components to form a protective film that effectively blocks the erosion of external factors. At the same time, its electrical insulation performance can avoid problems such as short circuits between electronic components and improve the reliability and service life of electronic components.
3. Unique advantages of hot melt adhesive film
The reason why hot melt adhesive film can stand out among many adhesives and is widely used in various fields is that it has many unique advantages.
3.1 Fast curing and efficient production
In industrial production, production efficiency is one of the important goals pursued by enterprises, and hot melt adhesive film has obvious advantages in this regard. Compared with traditional solvent-based adhesives, hot melt adhesive film cures very quickly. Solvent-based adhesives rely on the volatilization of solvents to achieve curing, a process that often takes several hours or even longer, and the curing time is also affected by factors such as ambient temperature and humidity. The curing process of hot melt adhesive film is a physical change that can be completed by simply lowering the temperature. Generally, it can be completely cured within a few seconds to tens of seconds after heating and laminating, forming a strong bond.
Under the same production conditions, the production efficiency of hot melt adhesive film for bonding is 5-10 times that of solvent-based adhesives. This advantage is particularly prominent in large-scale industrial production. Take automobile manufacturing as an example. On the assembly line of automobile interiors, a large number of parts need to be bonded, such as dashboards, door interior panels, seats, etc. If traditional adhesives are used, each bonding point needs to wait for a long time to cure, which will seriously affect the progress of the entire production line. With hot melt adhesive film, it only takes a dozen seconds from heating and laminating to curing, which greatly shortens the production cycle. After using hot melt adhesive film, the daily output of an automobile interior assembly line can be increased by more than 30% compared with the original, which greatly reduces the production cost and improves the economic benefits of the enterprise.
In the production of electronic products, the advantage of fast curing is also obvious. For example, in the assembly process of mobile phone screens, the screen needs to be bonded to the body. The use of hot melt adhesive film can complete the curing within a few seconds, ensuring that the subsequent production process can proceed smoothly and avoiding the production stagnation caused by waiting for curing.
3.2 Wide adaptability to substrates
Hot melt adhesive film has good bonding ability to various substrates, which is another major advantage. Whether it is metal, plastic, wood, or paper, cloth, leather, etc., hot melt adhesive film can form an effective bond with it to achieve a close connection between different materials.
The surface of metal materials is usually smooth and has a certain hardness. Traditional adhesives are often difficult to form a strong bond with them. However, after the hot melt adhesive film is heated and melted, it can well infiltrate the metal surface and form a strong intermolecular force with the metal surface, thereby achieving a strong bond. In the production of hardware products, hot melt adhesive film can bond metal accessories with other materials, such as bonding metal brackets with plastic panels to make the shells of various mechanical equipment.
There are many types of plastic materials, and the performance of different types of plastics varies greatly, which brings certain difficulties to bonding. However, hot melt adhesive film can select the appropriate type for bonding according to the characteristics of different plastics. For example, for non-polar plastics such as polyethylene (PE) and polypropylene (PP), although their surface energy is low and bonding is difficult, effective bonding can still be achieved by selecting hot melt adhesive film specially designed for these materials. In the production of plastic toys, hot melt adhesive film can bond plastic parts of different colors and shapes together to make various exquisite toys.
Wood is a porous material. When traditional adhesives are bonded to wood, they are prone to problems such as excessive penetration and waste of glue. After heating and melting, the hot melt adhesive film can evenly cover the surface of the wood, fill the pores on the surface of the wood, form a good bonding interface, and the amount of glue is easy to control, and there will be no excessive penetration. In furniture manufacturing, hot melt adhesive film is widely used for bonding solid wood boards and artificial boards, fixing wood and metal accessories, etc., and the furniture produced has a firm structure and beautiful appearance.
Hot melt adhesive film also has a very good bonding effect on materials such as paper, cloth, and leather. In book binding, the use of hot melt adhesive film can quickly and firmly bond the pages together, and the bound books are flat and beautiful, and it is not easy to fall off the pages; in clothing production, it can bond different fabrics together to achieve seamless splicing and improve the quality and comfort of clothing.
3.3 Environmental protection and economy
With the continuous improvement of people's environmental awareness and the increasingly stringent environmental protection regulations, the environmental protection performance of adhesives has received more and more attention. Hot melt adhesive film has significant advantages in environmental protection. It does not contain any solvents during production and use, and will not release harmful volatile organic compounds (VOCs) such as formaldehyde and benzene, avoiding pollution to the environment and operating The harm to the health of personnel. Traditional solvent-based adhesives release a large amount of VOCs during production and use. These substances will not only pollute the atmospheric environment and form environmental problems such as haze, but also damage the respiratory system and skin of operators who have long-term contact.
At the same time, hot melt adhesive film generates less waste during use. Because it is in the form of a film, it can be precisely cut as needed to avoid the waste of adhesive. Moreover, for some waste after bonding, the hot melt adhesive film can be separated from the bonded material by heating to achieve material recycling, which is in line with the development concept of circular economy.
In terms of economy, hot melt adhesive film also has obvious advantages. Its transportation cost is low. Since hot melt adhesive film does not contain solvents and is not a dangerous good, it does not need to comply with special regulations for the transportation of dangerous goods during transportation. The transportation method is more flexible and can be selected by road, rail, sea and other transportation methods. In addition, the packaging requirements during transportation are relatively simple, which reduces the transportation cost. Its storage cost is also low. Hot melt adhesive film does not require special storage conditions. It only needs to be stored in a dry place at room temperature away from light. It does not need refrigeration or special ventilation equipment like some adhesives, which saves storage costs.
In terms of use cost, the unit area usage of hot melt adhesive film is accurate and can effectively control the amount of adhesive used. Compared with traditional adhesives, its usage is more economical. Generally, only a few dozen grams of hot melt adhesive film per square meter of bonding area can achieve a good bonding effect. Moreover, due to its fast curing speed, it can improve production efficiency and reduce labor costs and equipment occupancy costs in the production process. Overall, the cost-effectiveness of hot melt adhesive film is higher than that of traditional adhesives, which can bring better economic benefits to enterprises.
4. Application fields of hot melt adhesive film
The application field of hot melt adhesive film is very wide, covering almost all aspects of industrial production and daily life. It plays an important role in different fields.
4.1 Packaging industry: the "invisible guard" protecting products
In the packaging industry, the application scenarios of hot melt adhesive film are very wide. In food packaging, it can be used to seal biscuit boxes, chocolate boxes, etc., to ensure the sealing of the packaging and prevent food from getting damp and deteriorating. At the same time, its good bonding effect can also ensure that the packaging is not easy to fall apart during transportation and sales. In terms of pharmaceutical packaging, the packaging of pharmaceuticals needs to have high safety and stability. The characteristics of hot melt adhesive film without solvent residue make it an ideal choice for pharmaceutical packaging and can effectively protect the quality of pharmaceuticals. In electronic product packaging, it can bond foam cushioning materials with cartons to provide good shock protection for electronic products and prevent products from being damaged during transportation. Hot melt adhesive film can also enhance the aesthetics of packaging and make products more attractive.
These cushioning materials are firmly bonded to cartons, packaging boxes, etc. to form a complete protection system, providing all-round protection for electronic products. For example, in the packaging of smart phones, hot melt adhesive film can bond the foam groove where the mobile phone is placed with the packaging box to ensure that the mobile phone will not shake during transportation, avoiding problems such as screen breakage and component damage. For some precision electronic components, such as chips and resistors, hot melt adhesive film is also used to fix them on anti-static packaging materials during packaging to prevent the components from being damaged by collisions during transportation and storage, and it can also play an anti-static role.
In gift packaging, the application of hot melt adhesive film can enhance the beauty and grade of gifts. Gift packaging often focuses on the exquisiteness and uniqueness of the appearance. Hot melt adhesive film can achieve the bonding of various complex shapes, such as the production of three-dimensional packaging boxes, the fixing of ribbons and packaging boxes, etc., and no obvious traces will be left after bonding, making the gift packaging more exquisite.
4.2 Textile and clothing industry: the "bonding power" behind fashion
In the textile and clothing industry, hot melt adhesive film is a "bonding power" hidden behind fashion. It not only changes the traditional clothing processing technology, but also brings new improvements to the design and quality of clothing.
In terms of seamless splicing of clothing, the traditional sewing process requires sewing the fabrics together with needles and threads, which will leave obvious stitches on the surface of the fabric, which not only affects the beauty of the clothing, but also may rub the skin during wearing, causing discomfort. When using hot melt adhesive film for seamless splicing, you only need to sandwich the hot melt adhesive film between two pieces of fabric. By heating and pressurizing, the fabrics can be tightly bonded, and the joints are flat and smooth without any stitches, which greatly improves the beauty and comfort of the clothing. This process is widely used in high-end underwear, sportswear, swimwear and other fields.
In terms of functional fabric lamination, as people's demand for clothing functionality continues to increase, various functional fabrics have emerged, such as windproof fabrics, waterproof fabrics, and warm fabrics. In order to meet different wearing needs, it is often necessary to compound multiple functional fabrics together to form fabrics with comprehensive performance. Hot melt adhesive film plays a key role in this process. It can firmly bond different functional fabrics together without affecting the original functionality of the fabrics. For example, when the windproof fabric and the warm fabric are laminated, the hot melt adhesive film can form a uniform bonding layer between the two fabrics, which not only ensures the windproof performance of the fabric, but also locks the air and enhances the warming effect; when the waterproof fabric and the breathable fabric are laminated, the bonding of the hot melt adhesive film will not block the breathable micropores of the fabric, ensuring that the clothing can maintain good breathability while being waterproof.
In terms of fixing embroidered badges, cloth patches, etc., the traditional method is to fix them on the clothing by sewing. This method is not only inefficient, but also the stitches are easily skewed, affecting the beauty of the clothing. When using hot melt adhesive film for fixing, you only need to pre-paste the hot melt adhesive film on the back of the embroidered badge or cloth patch, and then heat and pressurize it to quickly and firmly fix it on the clothing. This method is not only efficient, but also the embroidered badge or cloth patch after bonding is flat and fits well, and will not curl or fall off, which greatly improves the overall quality of the clothing.
In terms of fixing clothing accessories, such as zippers, buttons, Velcro, etc., hot melt adhesive film can also play an important role. In the installation of zippers, the traditional method is to fix the zipper to the fabric by sewing, which requires skilled technology to ensure that the zipper is installed flat. With hot melt adhesive film, you only need to apply the hot melt adhesive film on the edge of the zipper and then heat and bond it with the fabric to quickly fix the zipper. The zipper is flat and firm after installation, and the operation is simple and convenient. For some invisible buttons, hot melt adhesive film can bond the two sides of the button to the fabric separately to achieve the invisible effect of the button, making the surface of the clothing neater and more beautiful.
4.3 Electronic and electrical industry: "Reliable partner" for precision connection
The electronic and electrical industry has extremely high requirements for the connection accuracy and reliability of parts. Hot melt adhesive film has become a "reliable partner" for precision connection in this industry with its excellent performance.
In terms of fixing electronic components, electronic equipment contains a large number of electronic components, such as resistors, capacitors, inductors, chips, etc. These components need to be firmly fixed on the circuit board to ensure the normal operation of the electronic equipment. Traditional fixing methods mainly include welding and screw fixing. Welding requires high-temperature heating, which may damage some heat-sensitive components, and welding slag will be generated during the welding process, affecting the performance of electronic equipment; screw fixing requires drilling holes on the circuit board, which will damage the structure of the circuit board, and the operation is cumbersome and inefficient. To fix electronic components with hot melt adhesive film, just cut the hot melt adhesive film into a suitable size and place it between the component and the circuit board. By heating and pressurizing, the components can be quickly fixed. The bonding strength of the hot melt adhesive film is moderate, which can not only ensure that the components will not loosen during use, but also can be easily removed by heating when the components need to be repaired or replaced, without causing damage to the circuit board and components.
In the assembly of the display screen, the display screen is an important part of the electronic equipment, and its assembly quality directly affects the display effect and service life of the equipment. Hot melt adhesive film is mainly used for fixing the frame, laminating the touch screen and the display screen in the assembly of the display screen. In terms of frame fixing, the frame of the display screen needs to be closely combined with the fuselage to prevent dust and moisture from entering the inside of the display screen and affecting the display effect. Hot melt adhesive film can firmly bond the frame to the body to form a good sealing effect, and the bonded frame is flat and beautiful, which will not affect the appearance of the display. In the bonding of the touch screen and the display, the adhesive is required to have good light transmittance and bonding strength to ensure the sensitivity of the touch screen and the clarity of the display effect. Some transparent hot melt adhesive films, such as TPU hot melt adhesive film, PES hot melt adhesive film, etc., have excellent light transmittance, which can meet the requirements of the bonding of the touch screen and the display, and their high bonding strength can ensure that the touch screen and the display will not separate during long-term use.
In terms of circuit board protection, the circuit board is the core component of electronic equipment and is easily damaged by external factors such as dust, moisture, and vibration. Hot melt adhesive film can be used as a protective film for the circuit board, covering the surface of the circuit board to form a tough protective layer to effectively block the erosion of external factors. For example, in automotive electronic circuit boards, due to the violent vibration and temperature changes during driving, the circuit board is prone to problems such as loose solder joints and circuit oxidation. Using hot melt adhesive film to cover the surface of the circuit board can play a role in shockproof, moisture-proof and anti-oxidation, and improve the reliability and service life of the circuit board.
4.4 Automobile manufacturing industry: the "key link" of automobile assembly
Automobile manufacturing is a complex system engineering involving the assembly of many parts. Hot melt adhesive film plays the role of "key link" in the automobile assembly process, providing a strong guarantee for the comfort, safety and reliability of the car.
In the assembly of automobile interiors, the automobile interiors include seats, dashboards, door panels, ceilings, etc. The assembly quality of these parts directly affects the comfort and beauty of the car. Hot melt adhesive film is widely used in automobile interior assembly, such as the bonding of seat fabrics and sponges, the bonding of dashboard skins and skeletons, and the fixing of door panel decorative strips. In the production of seats, the traditional method is to fix the fabrics and sponges by sewing, which will leave stitches on the surface of the fabrics, affecting the beauty of the seats, and the sewing process will cause certain damage to the fabrics, reducing the strength of the fabrics. Using hot melt adhesive film to bond seat fabric and sponge can not only achieve seamless bonding, make the seat surface smoother and more beautiful, but also avoid damage to the fabric and improve the durability of the seat.
In the connection of automobile body parts, the automobile body is composed of many parts, such as doors, engine hoods, trunk lids, etc. The connection of these parts needs to have high strength and sealing. Hot melt adhesive film can be used for welding assistance and sealing of body parts. During the welding process of the body, there may be gaps at the joints of some parts, affecting the welding quality and the sealing of the body. Use hot melt adhesive film to pre-coat the joints. During the welding heating process, the hot melt adhesive film will melt and fill the gaps to form a good sealing effect, and at the same time, it can also improve the strength of the weld. For example, in the welding of car doors, using hot melt adhesive film to assist welding can effectively prevent rain, dust, etc. from entering the car and improve the sealing of the car.
5. Key points for the use of hot melt adhesive film
In order to give full play to the bonding performance of hot melt adhesive film and ensure the bonding quality, the following points need to be paid attention to during use.
5.1 Temperature control: the key to accurately grasp melting and curing
Temperature is one of the key factors affecting the bonding effect of hot melt adhesive film. Different types of hot melt adhesive films have different suitable temperature ranges. Only within this temperature range can the hot melt adhesive film fully melt and exert the best bonding performance.
The melting temperature of EVA hot melt adhesive film is generally between 80-120℃. During use, the heating temperature needs to be controlled within this range. If the temperature is too low, the EVA hot melt adhesive film cannot be fully melted, the fluidity and viscosity are insufficient, and it cannot well infiltrate the surface of the bonded material, resulting in insufficient bonding strength; if the temperature is too high, exceeding 150℃, the EVA hot melt adhesive film may decompose and age, produce odor, and also reduce its bonding performance, and may even damage the bonded material, such as deforming some plastic materials,Discoloration, etc.
The melting temperature of PA hot melt adhesive film is relatively high, generally between 120-180℃. Since PA hot melt adhesive film has good temperature resistance, it requires a higher heating temperature to fully melt it during use. If the temperature is not enough, the viscosity of PA hot melt adhesive film cannot be fully exerted, and the bonding effect is not good; but if the temperature is too high, exceeding 200℃, it will also cause the performance of PA hot melt adhesive film to decline and affect the stability of bonding.
The melting temperature of TPU hot melt adhesive film is usually between 100-160℃, and the specific temperature will vary depending on the hardness and brand of TPU. When using, it is necessary to control the heating temperature according to the specific product parameters to ensure that the TPU hot melt adhesive film can be fully melted and will not decompose due to excessive temperature.
The melting temperature of PES hot melt adhesive film is relatively high, generally between 180-240℃, because PES material has excellent heat resistance. During use, the heating temperature must be guaranteed to reach its melting temperature, otherwise effective bonding cannot be achieved. However, it should also be noted that the temperature should not be too high, so as to avoid the decomposition of the PES hot melt adhesive film, affecting its bonding performance and electrical insulation performance.
In actual operation, it is necessary to select appropriate heating equipment and temperature parameters according to the type of hot melt adhesive film and the characteristics of the bonded material. Commonly used heating equipment includes hot air guns, heating rollers, ovens, etc. For some small bonding operations, hot air guns can be used for local heating, and the heating temperature can be controlled by adjusting the temperature and distance of the hot air gun; for large-scale industrial production, heating rollers or ovens are usually used for heating. These devices can accurately control the temperature and ensure the uniformity of heating.
At the same time, it is also necessary to pay attention to the control of heating time. If the heating time is too short, the hot melt adhesive film may not be fully melted; if the heating time is too long, the bonded material may be overheated and damaged. Generally speaking, the heating time needs to be determined based on factors such as the thickness of the hot melt adhesive film and the power of the heating equipment to ensure that the hot melt adhesive film can be completely melted and infiltrated on the surface of the bonded material.
5.2 Pressure application: a necessary means to ensure close fit
During the bonding process of hot melt adhesive film, applying appropriate pressure is a necessary means to ensure close fit between the bonded material and the hot melt adhesive film. Pressure can make the molten hot melt adhesive film better infiltrate the surface of the bonded material, remove the air in the bonding interface, and improve the bonding strength and sealing.
Different bonded materials and bonding scenarios have different requirements for pressure. For some softer materials, such as paper, cloth, leather, etc., the required pressure is relatively small, generally between 0.1-0.5MPa. For example, in the bonding of clothing fabrics, using a heated roller to apply a pressure of 0.2-0.3MPa can make the hot melt adhesive film fit closely with the fabric and achieve a good bonding effect. If the pressure is too high, the fabric may deform and wrinkle, affecting the appearance and performance of the product.
For some harder materials, such as metal, plastic, wood, etc., the required pressure is relatively large, generally between 0.5-2MPa. For example, in the bonding of metal parts, a pressure of 1-1.5MPa needs to be applied to ensure that the hot melt adhesive film can fully fill the tiny gaps on the metal surface and form a strong bond. If the pressure is insufficient, there may be air in the bonding interface, resulting in a decrease in bonding strength and easy to fall off.
When applying pressure, it is necessary to ensure the uniformity of the pressure. If the pressure is uneven, it may cause the hot melt adhesive film to be unevenly distributed on the surface of the bonded material, with some parts firmly bonded and some parts loosely bonded, affecting the overall bonding quality. In large-scale production, hydraulic presses, pneumatic presses and other equipment are usually used to apply pressure, which can ensure the uniformity and stability of pressure; in small operations, manual pressure tools such as clamps and pressure rollers can be used, but the operator needs to pay attention to the uniformity of the applied pressure.
The time of applying pressure also needs to be coordinated with the heating time. Generally, pressure is applied after the hot melt adhesive film is completely melted, and it is maintained for a certain time until the hot melt adhesive film begins to solidify. This ensures that during the curing process of the hot melt adhesive film, the bonded material can be closely attached to the hot melt adhesive film, thereby improving the bonding effect. The pressure holding time is usually from a few seconds to tens of seconds, and the specific time will be determined according to the type, thickness and characteristics of the hot melt adhesive film.
5.3 Bonding time: Just the right bonding guarantee
The bonding time refers to the time that the bonded material and the hot melt adhesive film are in contact under heating and pressure conditions. It is closely related to temperature and pressure and is one of the important factors to ensure bonding quality.
Under certain temperature and pressure conditions, if the bonding time is too short, the hot melt adhesive film has melted, but it does not have enough time to fully infiltrate the surface of the bonded material, and it cannot form sufficient intermolecular forces with the bonded material, resulting in insufficient bonding strength, and it is easy to have problems such as weak bonding and falling off. For example, when using EVA hot melt adhesive film to bond paper, if the bonding time is only 1-2 seconds, the paper may not be firmly bonded and easily separated.
If the bonding time is too long, the hot melt adhesive film and the bonded material may be adversely affected under the continuous action of high temperature and pressure. For the hot melt adhesive film, long-term high temperature may cause it to decompose and age, reducing the bonding performance; for the bonded material, some heat-sensitive materials, such as plastics and paper, may deform and discolor due to long-term heat, affecting the quality of the product. For example, when using hot melt adhesive film to bond plastic film, if the bonding time is too long, the plastic film may shrink and wrinkle.
Therefore, in practical applications, it is necessary to reasonably determine the bonding time according to the type of hot melt adhesive film, heating temperature, applied pressure and the characteristics of the bonded material. Generally speaking, for thinner hot melt adhesive films and softer bonded materials, the bonding time can be relatively short, usually 3-10 seconds; for thicker hot melt adhesive films and harder bonded materials, the bonding time needs to be relatively long, usually 10-30 seconds.
During the operation, the best bonding time can be determined by experiment. First, set a preliminary bonding time, conduct a bonding test, then test the bonding strength and the appearance quality of the bonded material, and gradually adjust the bonding time according to the test results until the best bonding effect is achieved. At the same time, during the production process, it is necessary to maintain the stability of the bonding time to avoid the bonding time being long or short due to improper operation or equipment failure, which affects the consistency of product quality.
As an efficient, environmentally friendly and multifunctional adhesive, hot melt adhesive film has played an increasingly important role in industrial production since its advent with its unique properties and wide application. It uses thermoplastic polymers as the main component and achieves bonding by heating and melting. It has many advantages such as fast curing, wide adaptability of substrates, environmental protection and economy.
From the perspective of multiple types, EVA hot melt adhesive film is widely used and is the representative of basic models; PA hot melt adhesive film has superior performance and meets high-end needs; TPU hot melt adhesive film has balanced performance and is very useful in many fields; PES hot melt adhesive film performs well in the field of electronics. These different types of hot melt adhesive films provide a variety of choices for various industries.
In terms of application areas, hot melt adhesive films protect product safety in the packaging industry, promote fashion innovation in the textile and clothing industry, ensure the reliability of precision connections in the electronics and electrical industry, and maintain the comfort and safety of cars in the automotive manufacturing industry. They are present in every corner of industrial production and have become an indispensable "adhesive force".
